1. Field of the Invention
This invention relates to a crosslinked resin composition including a thermoplastic polyurethane, and a wire, a cable and a molded wire that are coated with the crosslinked resin composition.
2. Description of the Related Art
Conventionally, thermoplastic polyurethane (hereinafter, referred to as TPU) is widely used as a sheath material of a cable used in vehicles, robots and electronic devices, etc., due to its excellent mechanical characteristics and flexibility at low temperature. When various characteristics such as heat resistance, oil resistance and abrasion resistance, etc., are required depending on use environment, etc., of wires or cables and especially when heat resistance is required, a method of ensuring heat resistance by crosslinking TPU is used.
Meanwhile, when the wires or cables are connected to device components such as sensor, electrode terminals or other electronic circuits, peripheries of a connecting portion therebetween and the vicinity thereof are covered by a resin molded body for waterproofing the connecting portion.
When a cable is used for, e.g., an anti-lock braking system (hereinafter, referred to as ABS) for vehicle, heat resistance and waterproof properties are required. In an ABS which, as a vehicle safety control system, is composed of a wheel speed sensor, an electronic control unit and a hydraulic unit, the wheel speed sensor is provided on a wheel. Therefore, a cable connecting a sensor to a system is used under extreme conditions and use of a cable having heat resistance is an essential condition. In general, a connecting portion between a sensor and a cable is covered by a resin molded body for the purpose of waterproof and polyamide having high heat, impact and oil resistances is often used for the resin molded body.
In order to prevent contact failure due to the influence of use environment, it is required to improve especially waterproof of the cable connecting portion, i.e., air tightness between an outermost insulation of wire or a sheath of cable and a resin molded body.
For example, WO2005/013291 has proposed a method in which a mixed resin composition of thermoplastic polyurethane and thermoplastic polyester, as a sheath material of ABS sensor cable, is crosslinked to improve thermal adhesiveness with a resin molded body composition.